Process for covering at least two cores with the same jacketing material

ABSTRACT

A plurality of cores are covered with the same jacketing material by passing the cores through respective dies of a plate, while flowing the jacketing material through sub-channels in the plate and into coating relationship with the cores. Any of the sub-channels can be shut off by diverting the jacketing material a flow diverting path without affecting the flow in the other sub-channels.

This application is a division of application Ser. No. 07/846,908, filedMar. 6, 1992 now U.S. Pat. No. 5,249,945.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to methods and apparatus for covering a core witha jacketing material as the core passes through a tool such as a die.

2. Description of the Prior Art

It is known to jacket a complex material comprised of a plastic jacketand a core which is sensitive at the extrusion temperature of thejacket. It is also known to jacket a metal core, especially anelectrical cable, by extrusion.

All the known processes for carrying out these jacketing operations onlycarry out the jacketing of a single core. In order to cover severaldifferent (or identical) cores with the same jacketing material, it isnecessary to stop the extrusion of the jacket in order to clean, orindeed change, the die. It may also be necessary to stop the jacketingoperation to modify the parameters of the extruder and of the attachedequipment.

SUMMARY OF THE INVENTION

The present invention relates to a device adaptable to any system whichsupplies the device with molten material, and wherein the device iscapable of receiving at least two tools, such as dies.

The invention concerns more particularly an extruder head, called amulti-function head, making it possible to receive at least two diestraversed by identical or different cores and enabling all of the coresto be covered by the same jacketing material.

The cores may be constituted by fluid or solid materials capable ofpassing through the die.

The jacketing or covering material may comprise any material capable ofbeing extruded or which can be made into a film.

This device and the process which results therefrom are especiallyapplicable to the manufacture of at least two complex materialscomprised of identical or different cores made from plastic material,possibly reinforced by fibers, and which are coated by the samejacketing material. That jacketing material preferably comprises athermoplastic resin whose melting point is substantially in the vicinityof or greater than that of the constituent materials of the cores.

The constituent materials of the cores may be thermoplastic resins whichare identical to or different from those constituting the jacketingmaterial.

The apparatus comprises a plate having at least two cavities forsupporting a tool through which a core may pass. A main channel extendsinto the plate and is adapted to be connected to an extruder forreceiving a flow of jacketing material. At least two sub-channels extendfrom the main channel to respective ones of the cavities.

Preferably, the plate comprises two plate sections joined together.

A valve is preferably disposed in each sub-channel for controlling theflow of jacketing material. A flow diverting path preferablycommunicates with each sub-channel. Each valve is operable to divert theflow of jacketing material from its associated tool to its associatedflow diverting path to terminate the flow of jacketing material to theassociated tool without affecting the flow of jacketing material toanother tool.

The present invention also relates to a process of covering at least twocores with the same jacketing material. The process comprises passingthe cores through respective tools mounted in a plate while flowing aplastic resin through the plate and the tools and into coveringrelationship with the cores.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the invention will become apparent fromthe following detailed description of the preferred embodiment thereofin connection with the accompanying drawings, in which like numeralsdesignate like elements, and in which:

FIG. 1 is a perspective view of a core-jacketing plate according to afirst embodiment of the invention;

FIG. 2 is a view similar to FIG. 1 of a second embodiment of theinvention;

FIG. 3 is a sectional view taken along the line 3--3 in FIG. 4 with thepipette removed;

FIG. 4 is a sectional view taken along the line 4--4 in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

A jacketing device comprises a substantially cylindrical plate 1 inwhich at least two cavities 2 of substantially cylindrical shape areformed. A junction tube or pipette 3 is disposed in the plane of theplate and is bolted into the body of the plate 1.

The junction tube 3 makes it possible to link the plate with at leastone extruder, or with any system supplying the plate with moltenjacketing material. The junction tube 3 communicates with a centralchannel 4 located inside of the plate and which extends to the center ofthe plate.

According to the invention, each cavity may receive a die F which can becombined with an injector and with a system for conditioning the jacket.

Each cavity 2 may especially receive a tool such as described inEuropean Patent 188,939 whose content is incorporated by referenceherein.

A more preferred embodiment of the invention is depicted in FIGS. 2-4wherein the device comprises two substantially cylindrical platesections A and B which fit against each other in order to form a plate Csuch as shown diagrammatically in FIG. 2.

In this device, the junction tube or pipette 3 may advantageously befixed to the circumferential edge of the lower plate section A. Thecentral channel 4 is also formed in that lower plate section A. Theaxial lengths of the cavities 2, however, are formed partially by eachof the plate sections A, B, as is shown in FIG. 3.

The cavities 2 may be disposed at the periphery of the plate C in acircular arrangement as shown in FIGS. 1 and 2.

Each cavity 2 is connected to the main or central channel 4 via asub-channel 5 the circumference of which is formed partially by eachplate section A, B. The sub-channel 5 may be provided with a valve inthe form of a purge key 6 and at least one micrometer screw 7, enablingthe flow rate of the jacketing material to be regulated at the entry ofthe feed system of the die.

Each sub-channel 5 may be provided with a pressure indicator locatedpreferably between the micrometer screw 7 and the purge key 6.

The purge keys 6 communicate with respective flow diverting paths 8,shown in broken lines in FIG. 3. Each path 8 is provided with a purgeflow rate-limiting micrometer screw 9 which keeps the pressure constantin the sub-channel 5 downstream of the screw 7 and cancels the flowwhich exists in the "working" purge-key position.

The plate 1 may be fixed to the exit of an extruder by means of aclamping or coupling nut 10 (shown in FIG. 4) which engages the pipette3 bolted to the plate A, thus producing a leak-tight linkage between thebarrel of the extruder and the main or central feed channel 4 whileallowing a rotational freedom of the plate about the axis of the pipette3.

According to the invention, the number of cavities 2 in which a die F,or any other tool, may be received is at least two. However, dependingon the type and complexity of the cores to be jacketed, it is possibleto envisage a greater number of cavities, and it would not be outsidethe scope of the invention if this number were greater than 10. With aconcern for clarity, the device shown in FIGS. 1, 2 and 3 comprises onlyfive cavities.

Each die F and/or other tool is adjusted in the cavity in such a mannerthat the axis of the sub-channel 5 is aligned with the entry hole 14 ofthe die F. For this purpose, lower and upper clamping nuts 11, 12 areused so as to position the die-entry hole 14 opposite the entry channelfor the infeed of the covering material. These two nuts are then lockedin order to immobilize the die in its cavity.

The device according to the invention may carry out, equally well, thecovering of cores 15 traveling downwards or upwards through the die.

The purge keys 6 may assume several positions X, Y, Z as shown in FIG. 3to control the flow of jacketing material.

When the purge key 6 is in a "die feed" position shown in FIG. 3, thepurge key 6 unblocks the associated sub-channel 5 and blocks theassociated path 8. Hence, the flow of jacketing material issuing from anextruder and flowing through the pipette 3 and then through the centralchannel 4 may enter a die F by way of the sub-channel 5. This applies,for example, to the dies F2 and F4 of FIG. 3.

When the purge key 6 is in an "individual purge" position Y shown inFIG. 3, the purge key 6 communicates the associated sub-channel 5 withthe associated path 6. Therefore, the flow of jacketing material isdiverted from the sub-channel 5 to the path 8 (or to some other path ifprovided). This is the case, for example, for the sub-channels leadingto the dies F1 and F5 of FIG. 3. The jacketing material traveling inthis path 8 may advantageously be recycled, especially back into theextruder. Thus, the paths 8 may include individual outlets, or a commonoutlet which open at a side or circumferential edge of the plate C, andsuitably coupled to the extruder.

The ability to divert the flow of jacketing material to the path 8enables the parameters of the flow-blocked dies F1, F5 to be modified ifrequired, without halting or modifying the flow of jacketing materialbeing fed to the other dies F2, F4. The overall flow rates and/orpressures of the material fed to dies F2, F4 are thus maintained.

When the purge key 6 is in a "closed" position Z shown in FIG. 3, theassociated sub-channel 5 is completely closed. This case occurs when thecorresponding cavity 2 is not provided with a die or other tool, orwhenever the operation of the sub-channel 5 corresponding to this cavityis desired to be stopped for any reason.

The purge keys 6 may also assume intermediate positions between thepositions X, Y and Z to regulate the flows to the dies. The flowrate-limiting function of the micrometer screws 7 may be performed aswell by the purge key itself, thus acting as a "servo-valve".

According to the device in accordance with the invention, a die and/ortool change operation does not involve stopping the whole system. Also,the flow rate to the other dies is not adversely affected because when apurge key 6 is in the purge position Y, the flow of material through therespective path 8 will simulate the flow rate which had been flowing tothe die. Hence, the still-functioning dies will not "feel" any affectsof the shut-down of another die when the purge key associated with thelatter is maneuvered to an individual purge position.

Advantageously, all or part of the closing and opening operations of thepurge keys and of the micrometer screws may be regulated automatically.

The cavities of the multi-function head may be provided with heatingsystems 13 constituted especially by electrical resistance elementswhich may be modulated together or separately, thus providing a possibletemperature gradient adjusted to each die and/or tool.

By means of the device in accordance with the invention, it is possibleto manufacture at least two complex materials each covered by the samejacketing material (e.g., a plastic resin) and containing identical ordifferent cores.

According to the technique in question, all extrudable or film-formableplastic resins may be suitable for covering the cores.

They may, for example, be chosen from the group vinyl, styrene, acrylicor methacrylic, olefin polymers or copolymers, or also from fluorinatedresins, polyamides, polyesters, polycarbonates, cellulose propionates,polyphenylenesulphones, polyamideimides, polyimides, polyetherimides,polyethersulphones, polyetheretherketones and mixtures of thesecompounds as well as any film-formable substance.

The jacket may be constituted from a mixture of plastic resin andadditives such as colorants, mineral or vegetable flours havingcomplementary properties with respect to the constituents of the core.

The materials used for the core may be chosen from fluid or solidmaterials capable of flowing through a die and/or tool.

The core may be constituted by metallic, organic, inorganic andvegetable filaments, fibers and powders, and by mixtures of thesevarious constituents.

The materials used for the core may also be chosen from extrudableplastic resins used for the jacketing material.

By way of illustration of organic fibers which can be used in order toconstitute the core, polyamide, polyester, polyaryl and polyfluorinatedfibers will be mentioned.

By way of illustration of metallic filaments or fibers which can be usedin order to constitute the core, copper, aluminum and iron filaments, asa continuous length or broken up intermittently, will be mentioned.

By way of illustration of vegetable fibers which can be used in order toconstitute the core, cotton, wool, flax, hemp, silk and wood fibers willbe mentioned.

By way of illustration of inorganic fibers which can be used in order toconstitute the core, glass fibers, carbon fibers, ceramic fibers,especially fibers based on boron and silicon nitride, will be mentioned.

The organic and/or inorganic fibers may be impregnated with solid,porous or hollow fillers which may be constituted by powders, balls orlamellae, the fillers being organic, metallic or inorganic.

By way of illustration of such fillers, capable of impregnating theorganic and/or inorganic fibers which can be used in order to constitutethe core, polyamide or polymethyl methacrylate powders, glass or metalballs, graphite powders, metallic powders, such as molybdenum sulphide,glass spheres and metal spheres will be mentioned.

The process according to the invention is particularly suitable forjacketing cores which are sensitive at the extrusion temperature of thesingle jacketing material.

Such sensitive cores may be constituted, partially or completely, frominert and/or reactive powders and from active substances.

Concerning reactive powders, catalyst powders, blowing agents, enzymepowders, oxidizable powders, such as food powders, microorganismpowders, yeasts and mixtures of these various constituents, will bementioned.

Concerning active substances, essential oils, plant essences andvolatile or non-volatile fluid products will be mentioned.

Thus, for medical applications especially, it is possible to produce acomplex material constituted from a jacket, made from polyolefin loadedwith vegetable flour, such as corn flour, and from a core made frommineral powder impregnated with microorganisms.

The jacketing material may be the same as, or different from the corematerial, depending on the core to be jacketed.

The thickness of the covering jacket is limited by the properties of theextrudable or film-formable material. In jacketing applications, suchthickness does not usually exceed one millimeter. It is possible for thethickness to be thicker in other applications.

The diameter of the complex material produced by the process may varywidely. For composites, this diameter is not less than 0.1 mm and,preferably, lies between 0.5 and 5 mm.

The following example illustrates the invention:

Starting with a single-screw type extruder of B30-20D diameter, providedwith a multi-function head, equipped in accordance with the inventionwith 5 dies as described in European Patent 188,939, a jacket ofpolypropylene (homopolymer of propylene of melt index equal to 35 g/10min, measured at 230° C. with a load of 2.16 kg) is extruded at atemperature of 215° C. and an extrusion rate of 100 meters per minute inorder to cover, respectively, the following cores:

    ______________________________________                                        die 1       320 tex glass fiber                                               die 2       320 tex glass fiber impregnated with                                          FORAFLON PVDF powder                                              die 3       160 tex glass fiber impregnated                                               an ORGASOL 2002.D Nat polyamide                                               powder                                                            die 4       420 tex glass fiber impregnated                                               with polyamide powder (identical                                              to that of the jacketed material                                              in die 3).                                                        die 5       320 tex glass fiber.                                              ______________________________________                                    

The pressure of the dies lies between 5 and 30 bar.

For the dies 1, 2, 3 and 5, the core is directed downwards and for thedie 4 the core is directed upwards.

The rate of haul-off of the product from each die is a function of thedesired thickness and is on the order of 70 to 200 m/min.

The trial lasted 30 min. In Table I hereinbelow are indicated the weightpercentage of fiber, powder and jacket in the finished material.

                  TABLE I                                                         ______________________________________                                        Product From                                                                  the Die     Fiber       Powder   Jacket                                       ______________________________________                                        2           67          15       18                                           3           57          12       31                                           4           77          13       10                                           5                                                                             ______________________________________                                    

While the invention has been described in terms of the preferredembodiments, the skilled artisan will appreciate that variousmodifications, substitutions, omissions, and changes may be made withoutdeparting from the spirit thereof. Accordingly, it is intended that thescope of the present invention be limited solely by the scope of thefollowing claims.

What is claimed is:
 1. A process of covering at least two cores with thesame jacketing material, comprising:orienting a plate substantiallyhorizontally, said plate having at least two cavities extendingcompletely therethrough in a substantially vertical direction, toolsdisposed in respective ones of said cavities for guiding jacketingmaterial, a main channel disposed in said plate and extendingsubstantially horizontally to an outer circumference of said plate, andat least two sub-channels intersecting an inner end of said main channelat respective horizontally spaced locations, each sub-channel extendingsubstantially horizontally from its respective intersection location torespective ones of said tools; passing at least two cores throughrespective ones of said tools in substantially vertical directions; andcausing jacketing material in the form of plastic resin to sequentiallyflow:through said outer circumference and horizontally within said mainchannel, horizontally through said at least two sub-channels, and intosaid at least two tools and into covering relationship with said atleast two cores.
 2. Process according to claim 1, wherein said plasticresin is selected from a group comprising vinyl, styrene, acrylic ormethacrylic, olefin polymers or copolymers, fluorinated resins,polyamides, polyesters, polycarbonates, cellulose proprionates,polyphenylenesulphones, polyamideimides, polyimides, polyetherimides,polyestersulphones, polyetheretherketones and mixtures of thesecompounds.
 3. Process according to claim 1, wherein said core is a fluidor solid material capable of flowing through said tool.
 4. Processaccording to claim 1, wherein said core is selected from a groupcomprising metallic, organic, inorganic and vegetable filaments, fibersand powders and mixtures thereof.
 5. Process according to claim 4,wherein said organic fibers are selected from a group comprisingpolyamide, polyester and polyfluorinated fibers.
 6. Process according toclaim 4, wherein said metallic filaments are selected from a groupcomprising copper, aluminum and iron filaments.
 7. Process according toclaim 4, wherein said vegetable fibers are selected from the groupcomprising cotton, hemp, wool, flex, silk and wood fibers.
 8. Processaccording to claim 4, wherein said inorganic fibers are selected from agroup comprising glass fibers, carbon fibers and ceramic fibers. 9.Process according to claim 4, wherein said organic and/or inorganicfibers are impregnated with solid, porous or hollow fillers.
 10. Processaccording to claim 9, wherein said solid, porous or hollow fillers areselected from a group comprising organic, metallic or inorganic powders,balls and lamellae.
 11. Process according to claim 10, wherein saidorganic powders are selected from a group comprising polyamide powders,polymethyl methacrylate powders and graphite powders.
 12. Processaccording to claim 10, wherein said metallic powder comprises amolybdenum sulphide powder.
 13. Process according to claim 1, whereinsaid cores are sensitive at the extrusion temperature of said jacketingmaterial.
 14. Process according to claim 13, wherein said sensitivecores are selected from inert and/or reactive powders.
 15. Processaccording to claim 14, wherein said reactive powders are selected from agroup comprising catalyst powders, blowing agents, enzyme powders, foodpowders, microorganism powders and mixtures thereof.
 16. Processaccording to claim 14, wherein said inert powders are selected from agroup comprised of polyolefin powders and polyamide powders.